This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We initiated a study of lipid interactions of a synthetic peptide corresponding to the transmembrane domain (TM) of hemagglutinin (HA) from influenza virus. We are intrigued by a question of whether the TM plays a passive role, or is actively involved in HA-mediated membrane fusion. Recently it was shown that replacing the TM of HA with a glycophosphoinositol-linked lipid anchor results in hemifusion, but not complete fusion. Also replacing either the v-SNARE or t-SNARE (or both) peptidic anchors with a single lipid unit, prohibits lipid mixing in SNARE-mediated vesicle fusion. It was suggested that simply holding two vesicles together is not sufficient for membrane fusion, and a pulling force exerted on the membrane anchors might be important for the fusion activity.